Plasma reactor with a deposition shield

ABSTRACT

A reactor  20  includes a shield  50  which prevents the deposition of materials along a line-of-sight path from a wafer  26  toward and onto an electrode  32 , or a window  38  which couples an electrode  32  to a reaction chamber of the reactor  20 . The shield can be comprised of a conductor and/or an insulator. The shield can affect the character of a plasma generated in the reactor.

This case is a continuation-in-part of U.S. patent application Ser. No.08/985,730, filed on Dec. 5, 1997, entitled “Plasma Reactor with aDeposition Shield.”

FIELD OF THE INVENTION

The present invention is directed to a semiconductor processing reactorand in particular to a reactor which causes material to sputter from thewafer being processed.

BACKGROUND OF THE INVENTION

During semiconductor fabrication processes including but not limited toetch processes, material from a wafer may have a tendency to sputtertherefrom and deposit on various surfaces, including but not limited tocooler surfaces, of a reactor such as the walls of a reactor.Inductively coupled plasma reactors generally have a first powerelectrode which can be in the shape of a inductive coil which is coupledto the reactor chamber through a window which is generally comprised ofquartz. In such an arrangement, material sputtered from a wafer andtraveling in a direct line-of-sight, can strike and build-up on thevarious surfaces of the reactor including the walls and the window. Suchdeposits caused by sputtering and other mechanisms can adversely affectthe operation of the reactor. The build-up of such materials means thatthe reactor must be periodically shut down and the various surfaces areeither cleaned or replaced. Accordingly, there is a need to minimize theeffect of material sputtered from the wafer surface, which is depositedon the walls and window of the reactor. Further, there is a need tominimize the effect of materials deposited by any mechanism on thewalls, windows, and other surfaces of a reactor.

SUMMARY OF THE INVENTION

The present invention is directed to overcome the disadvantages of theprior art. In particular, the present invention is advantageously usefulfor semiconductor wafer processing operations that cause materials tosputter from the surface of a wafer. In particular, in the case of ainductively coupled plasma reactor having an electrode in the form of aninductive coil coupled to the reactor chamber through a power transferwindow, deposited materials, including but not limited to metals andother materials deposited by sputtering and other mechanisms, couldimpinge and collect upon the window reducing or eliminating the powercoupling from the inductive electrode.

Accordingly, it is an object of the present invention to provide amechanism whereby the sputtering of the materials from the wafer doesnot reduce or eliminate the power coupling from the inductive electrodeor any other electrodes.

It is another object of the present invention to provide a depositionshield that prevents the deposition of materials on a power transferwindow or an electrode. Deposition could occur through mechanisms suchas sputtering, condensation, and the like.

It is another object of the present invention to provide a depositionshield to intercept material sputtered from the wafer surface that isdirected toward the electrode and/or the window which couples theelectrode to the reaction chamber.

It is a further object of the present invention to provide a depositionshield that is in the direct line-of-sight or sputter path between thewafer and the electrode or window.

It is a further object of the present invention to provide for a reactorwhich has a longer operational mean time between shutdown formaintenance and cleaning.

Yet a further object of the present invention is to provide a shieldwhich is comprised of material which affects the character of a plasmaformed in the reactor.

Yet another object of the present invention is to provide a shield whichis comprised of one of a conductor and non-conductor such as aninsulator.

Still a further object of the present invention is to provide a shieldwhich allows an electrical field to continue through the shield from afirst chamber to a second chamber where a wafer is held by a chuck.

Yet another object of the present invention is to provide a shieldcomprised of, by way of example only, conductors such as aluminum,annodized aluminum, carbon (graphite), and carbon based compoundscontaining graphite.

In still a further object of the present invention, the shield iscomprised of an insulator including, by way of example only, one ofalumina, quartz, teflon, delrin, nylon, polyamide, and a supportstructure coated with an organic compound, and generally carbon basedcompounds (plastics).

Still a further object of the present invention is to provide a shieldwhich protects a wafer held on a chuck in a second chamber fromgeneration of a plasma.

In accordance with the invention, a plasma reactor includes an electrodewhich is used to create a plasma and a reactor chamber. The reactorincludes a chuck that is adapted to hold the wafer, which chuck islocated in the reactor chamber. The reactor further includes adeposition shield which is located in the reactor chamber in theline-of-sight path between the wafer and the electrode.

In another aspect of the invention, the deposition shield includes aplurality of louvers or slats.

In a further aspect of the invention, the deposition shield includes aplurality of overlapping louvers or slats which block the line-of-sightpath between the wafer and the electrode in order to block the path ofmaterials removed from the wafer, by methods including but not limitedto sputtering, and directed toward the electrode.

In yet a further aspect of the invention, the plasma reactor is aninductively coupled plasma reactor and the reactor includes a windowwhich shields the electrode from the reactor chamber. The depositionshield prevents materials from being deposited onto the window andthereby reducing or eliminating the power coupling from the inductiveelectrode which is coupled through the window to the reactor chamber.

In another aspect of the invention, the shield is comprised of materialwhich affects the character of the plasma.

In still another aspect of the invention, the shield is comprised of oneof a conductor and an insulator.

In another aspect of the invention, the plasma reactor includes atri-electrode reactor with a first electrode located at the top of thereactor, a second electrode located about the periphery of the chamber,and a third electrode located at the bottom of the chamber andassociated with the chuck which holds a wafer. The top electrode caninclude, by way of example only, a capacitively coupled electrode.

In another aspect of the invention and in particular with an inductivelycoupled plasma reactor, a device is provided for preventing thereduction or elimination of the power coupling of a inductive electrode,which is coupled to the reactor chamber through a window.

In another aspect of the invention, the deposition shield allows foreffective operation of ICP (Inductively Coupled Plasma) systems and ECR(Electron Cyclotron Resonance) systems.

Other aspects, objects and advantages of the invention will be evidentfrom a review of the specification, the claims and the appendeddrawings.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 a, 1 b, and 1 c depict a representative inductively coupledplasma reactors incorporating embodiments of the deposition shield ofthe invention.

FIG. 2 depicts an alternative embodiment of the deposition shield of theinvention.

FIGS. 3 a and 3 b depict yet further alternative embodiments of thedeposition shield of the invention.

FIGS. 4 a, 4 b, 4 c, and 4 d depict further alternative embodiments ofthe deposition shield of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 a, 1 b, and 1 c depict a plasma reactor 20 of the presentinvention. The plasma reactor in this particular embodiment is aninductively coupled plasma reactor. It is to be understood that theessence of the invention can be practiced in other types of reactorssuch as ECR, Helicon and other ICP reactors as well as capacitivelycoupled reactors. Thus, the invention is advantageous for any variety ofreactors which can perform a variety of operations and which can causethe deposition of materials from the surface of a wafer onto othersurfaces such as a power transfer window. The reactor 20 configured inthis embodiment to perform an etching process. The reactor 20 includes ahousing 22 and a reactor or etched chamber 24. A wafer 26 is positionedon a chuck incorporated with a bottom electrode 28. The chamber 24further includes a side peripheral electrode 30 which can be grounded orallowed to establish a floating potential as a result of the plasmadeveloped in the chamber 24. The reactor 20 includes an upper electrode32 which in this embodiment includes an inductor coil.

Preferably, the reactor 20 includes two A.C. power sources. A firstpower source 34 is connected to the upper electrode 32 and a secondpower source 36 is connected to the bottom electrode 28. Appropriatecircuitry for both connections may include matching networks. Further, acontroller 40 controls the sequencing of the first and second AC powersource 36, 38. In this embodiment, the first power source 34 is operatedin the megahertz range, and preferably operates at about 13.56 MHzalthough other frequencies in the MHz and GHz range can be used with thepresent invention. The second power source 32 preferably operates in theKHz range and is optimally operated at about 450 KHz and generally inthe range that is less than about 500 KHz. However, the second powersupply can also be operated into the MHz range. It is to be understoodthat ion energy increases toward the KHz range while ion densityincreases toward the MHz range. Further, the wafer electrode can haveapplied thereto mixed frequency power supplies such as power supplies inthe KHz and MHz ranges, or in the KHz and GHz ranges. The presentembodiment further includes a process gas inlet head 42 and process gasoutlet port 44. While the reactor chamber of FIGS. 1 a, 1 b, and 1 cdepict top pumped systems, it is to be understood other reactor systemswhich have process gas inlet and outlet ports in various other locationsof the reactor system, including but not limited to ports associatedwith a bottom chuck electrode, can benefit from the present invention.

A power transfer window 38, which is generally comprised of quartz orany other material which allows the power that is transferred throughthe inductive coil of upper electrode 32 to be coupled to the reactorchamber 24, is positioned adjacent to the inductive upper electrode 32.

The invention further includes a shield 50 which in the presentembodiment includes a plurality of louvers or slats 52 which arepositioned at a skewed angle with respect to the wafer 26 and the bottomelectrode 28. This shield can prevent the deposition of materials 10onto the power transfer window 38 so that power coupling with theelectrode 32 through the window is not reduced or eliminated. Thedeposition of materials can occur from a number of mechanism such assputtering, condensation, and the like. Although reference is made belowto sputter shields, such shields can prevent deposition by any of saidnumber of mechanisms.

In this embodiment of FIG. 1 a, the shield 50 interrupts a line-of-sightsputter path between a material sputtered from the wafer 26, and thewindow 38 and the induction coil 32. A particular sputter shield 50includes louvers 52 which overlap in order to block material sputteredfrom the wafer 26. In a preferred embodiment, the sputter shield 50 canbe comprised of quartz, ceramic, or other insulating materials which areappropriate to the reactor chamber. Conductors can also be used for theshield. The sputter shield 50 can in fact be analogized to a set ofVenetian blinds which have been partially opened. The sputter shield 50prevents materials and in particular metals from metal film on asemiconductor wafer 26 from being sputtered and deposited on the window38. Such metals could reduce or eliminate the coupling of power betweenthe inductive coil of upper electrode 32 and the reactor chamber 24.

As can be seen in FIG. 1 a, the deposition shield 50 is located in thispreferred embodiment mid-way through the reactor chamber 24 in order tocreate an upper chamber 51 in which the plasma is developed and lowerchamber 53 where the wafer is located and where the semiconductorprocessing occurs.

Thus, it is to be understood that with the shield positioned in FIG. 1 asubstantially divides the chamber to an upper chamber and a lowerchamber that such a reactor operates much in the way that a downstreamreactor operates. That is to say that while the shield prevents thesputtering or deposition of materials from the wafer back onto thecoupling window of 32, the shield also protects the wafer fromundesirable aspects of the plasma which could damage the wafer.

FIG. 1 b depicts an alternative embodiment of the invention of FIG. 1 awherein the deposition shield is placed adjacent to the window 38. Inthis embodiment, the shield 50 is placed above where a plasma wouldnormally form in the chamber and thus does not interfere with theformation of the plasma. However, the shield does prevent or greatlyreduce the deposition of materials onto the window 38, which depositionwould reduce or eliminate the power coupling of the power source throughthe window. As can be seen in FIG. 1 b, the shield 50 includes aplurality of louvers 57, 59. The louvers 57 slopes somewhat leftwardlyfrom a center of the induction coil 32 while the louvers 59 slopessomewhat rightwardly from the center of the induction coil 32.

FIG. 1 c depicts yet a further embodiment of the present inventionwherein the deposition shield 50 is incorporated into the window 38.Such incorporation can be for example provided when the window is madeout of quartz and the deposition shield Is provided through theformation of grooves directly into the window 38, with the grooves beingdirected much as the spaces between the louvers 57 and 59 of FIG. 1 bare oriented. Additionally, it is possible to cause a deposition shieldto be directly deposited on the window 38 in order to form a structuremuch as that shown in FIG. 1 c wherein grooves are formed directly intothe material of the window 38. By way of example only, a quartz windowcould be formed with the deposition of alumina thereupon in order toconstruct for example mini-louvers that would act as a depositionshield. Additionally, it is to be understood that other patterns can bedeposited on the window in order to form a deposition shield and bewithin the spirit and scope of the invention. These patterns would causeportions of the window 38 to be out of the direct line of sight of thewafer 26.

Another embodiment of the deposition shield 55 of the invention can beseen in FIG. 2. This deposition shield 55 includes first and secondcourses 54, 56 of individual louvers or slats 58 and 60 respectively.The slats of the first and second courses 54, 56, are parallel to thewafer 26. The slats 58 of course 54 overlap the ends of the slats 60 ofcourse 56. Such an arrangement provide a line-of-sight shield in orderto prevent sputtered or other materials from impinging upon anddepositing on the window 38 or in case of a capacitively coupledreactor, the upper electrode. The embodiment of the shield in FIG. 2 canbe placed in any of the three locations depicted in FIGS. 1 a, 1 b, andc.

FIGS. 3 a and 3 b depict yet an alternative embodiment of the shield 70of the invention. This shield includes first and second courses 72, 74of louvers or slats 76, 78, respectively. The first course 72 includes aplurality of louvers or slats 76 which are parallel to each other andskewed with one orientation with respect to the wafer 26. The secondcourse 74 includes the louvers or slats 78 which are parallel to eachother and skewed in another direction with respect to the semiconductorwafer 26. In a preferred embodiment using the configuration of FIG. 3 athe first course of slats 72 is skewed at an acute angle of about 45°and the second course 74° is skewed at an obtuse angle of about 135°.The ends of the slats 76, 78 overlap each other.

In FIG. 3 b, an alternative embodiment of the shield 70 is depictedwhich includes first and second courses 72, 74 of louvers or slats whichare configured somewhat like the louvers and slats shown in FIG. 1 b.That is to say that the first course 72 includes louvers or slats 76 and77 with louvers 76 directed somewhat leftwardly and louvers 77 directedsomewhat rightwardly. A second course 74 includes louvers and slats 78and 79 with louvers 78 directed somewhat rightwardly and louvers 79directed somewhat leftwardly.

In yet a further embodiment of the invention shown in FIGS. 4 a, 4 b, 4c, and 4 d. A shield 80 includes first and second courses 82, 84 oflouvers or slats 86 and 88 respectfully. From the side view of FIG. 4 a,the louver or slats look similar to those of FIG. 1 in that they arecomprised of a plurality of parallel louvers or slats inclined at anacute angle with respect to bottom electrode 28. Turning to FIGS. 4 band 4 c, it is evident that the louvers are specially configured, withmaterial eliminated in certain areas, in order to have a plurality oftabs 90 with respect to louvers 86 and a plurality of tabs 92 withrespect to louvers 88. The tabs 90 define spaces 94 locatedtherebetween. Spaces 94 are blocked or shielded by the tabs 92 of thelower course 88. Similarly, the tabs 92 include spaces 96 locatedtherebetween. These spaces 96 are shielded by the tabs 90 of the uppercourse 82. Accordingly, the embodiment of FIG. 4 a, 4 b, and 4 c, depicta deposition shield having a plurality of channels for the diffusion ofetchants and other process gases from the upper chamber of FIG. 1 a tothe lower chamber so that these etchants and other process gases canreact with the wafer.

With respect to FIG. 4 d, this includes first and second course 82, 84.First course 82 includes slats 86, 87, and second course 84 includesslats 88, 89. As with the embodiment of FIG. 1 b, slats 86 are somewhatleftwardly directed while slats 87 are somewhat rightwardly directed.Additionally, slats 88 are somewhat leftwardly directed while slats 89are somewhat rightwardly directed. Such an arrangement is advantageousin order to prevent deposition of materials on the power transfer window38.

With respect to FIGS. 4 a and 4 b, the shield 80 can be placed adjacentto or incorporated into the window in order to not interfere with theformation of the plasma therebelow in the chamber of the reactor, andafford deposition protection to the window in order to not reduce oreliminate the power coupling effect of the window.

The above FIGS. 1-4 d depict variations of an advantageous shield of theinvention. It is to be understood that the shield can be subject to wearand that it is designed to be replaceable, as are one or more of theelectrodes of the reactor.

In all the above embodiments, the shield, such as shield 50, can becomprised of various materials, such as for example a conductor, and anon-conductor such as an insulator in order to affect the generation ofplasma both. With the shield 50 consisting of a conductor, theelectrical field generated by the electrodes do not penetrate the shieldsuch that an electrical field is established in the upper chamber 51 andnot in the lower chamber 53 of FIG. 1 a. Additionally, adjusting thepressure and temperature of the chambers and the frequencies of theelectrodes relative to the lower chamber would affect the plasmadeveloped.

The shield of FIG. 1 a can isolate the plasma generation to the upperchamber 51. The use of such a shield blocks energized ions andultraviolet radiation, developed in the upper chamber, from damaging thewafer held in a chuck in the second chamber. The shield decouples theplasma generation which occurs in the upper chamber 51 from the etchingoperation which occurs in the lower chamber 53. Such an arrangement islike a downstream etch reactor where the plasma generation can belocated distantly from the actual etch site in order to avoid waferdamage from energized ions and radiation such as ultraviolet radiation.

With a conductive shield 50 placed adjacent to the window 38 (FIG. 1 b),plasma would form in the main chamber 57, below the deposition shield50. As a plasma is formed below the shield, the shield does notinterfere with the formation of plasma. Accordingly, there is nolessening of the plasma density with respect to the wafer 26.

A conductive shield can be comprised of a metal such as, by way ofexample only, aluminum, anodized aluminum, or carbon (graphite) or acarbon based compound containing graphite, or any other conductor whichwould not contaminate the wafer.

Alternatively, the shield in FIG. 1 a can be comprised of an insulatorwhich shields the second chamber from the plasma. Such an insulatingshield enables the reactor to act as a downstream etcher.

Still alternatively, the shields of FIGS. 1 b and 1 c can be comprisedof insulating materials. Further, the insulating shield positionedadjacent to the coupling window as indicated in FIG. 1 b, can beincorporated into the coupling window as indicated in FIG. 1 c.

The insulating shield can be comprised of a material such as for examplealumina, quartz, silicon, teflon, delrin, nylon, polyamide, and carbonbased compounds (plastics), and other organic materials. In addition, anonorganic support structure can be covered with organic materials inorder to form a shield.

It is to be understood that whenever any of the shields wear out, thatthe shields can be replaced with new shields.

INDUSTRIAL APPLICABILITY

The present invention is directed to providing a shield in order toensure that the deposition of materials from a wafer does not reduce oreliminate the effectiveness of power transfer windows used with anelectrode and/or the effectiveness of the reactor generally. Theelectrode can be used for example to create the plasma of the reactor.

Other features, aspects and objects of the invention can be obtainedfrom a review of the figures and the claims.

It is to be understood that other embodiments of the invention can bedeveloped and fall within the spirit and scope of the invention andclaims.

We claim:
 1. A shield for a reactor which is placed in a line-of-sightpath between a wafer to be processed and one of an electrode and a powertransfer window, in order to block the path of material from the waferdirected toward said one of said electrode and said power transferwindow wherein said shield is part of said one of said electrode andsaid power transfer window, said shield comprising: a plurality oflouvers.
 2. The shield of claim 1 wherein: including another pluralityof louvers which overlaps said plurality of louvers.
 3. The shield ofclaim 2 wherein: at least some of said louvers include tabs, and atleast some of the louvers of said another plurality of louvers includetabs.
 4. The shield of claim 2 wherein: at least some of the louvers ofsaid plurality of louvers include first tabs with spaces locatedtherebetween, and at least some of the louvers of said another pluralityof louvers include second tabs with spaces located therebetween; andwherein at least some tabs from the plurality of louvers are positionedto cover at least some of the spaces between the another plurality oflouvers.
 5. The shield of claim 1 wherein: at least some of the louversinclude tabs.
 6. The shield of claim 1 wherein: said material of saidshield is comprised of one of a conductor and an insulator.
 7. Theshield of claim 1 wherein: said material of said shield is an insulatorwhich allows a magnetic field to continue through the shield.
 8. Theshield of claim 1 wherein: said shield is comprised of one of aluminum,anodized aluminum, carbon, and carbon based compounds.
 9. The shield ofclaim 1 wherein: wherein said shield is comprised one of alumina,quartz, silicon, polytetrafluoroethylene, delrin, polyamide, and asupport structure coated with an organic compound.
 10. The shield ofclaim 1 wherein: said shield is comprised of an organic compound.
 11. Ashield for a reactor which is placed in a line-of-sight path between achuck which is adapted to hold a wafer to be processed and an electrodein order to block the path of material from the wafer directed towardthe electrode, and said shield is an integral part of said electrode,said shield comprising: a plurality of louvers.
 12. The shield of claim11 and including: another plurality of louvers which overlaps saidplurality of louvers.
 13. The shield of claim 12 wherein: at least someof the louvers of said plurality of louvers include tabs, and at leastsome of the louvers of said another plurality of louvers include tabs.14. The shield of claim 12: at least some of the louvers of saidplurality of louvers include first tabs with spaces locatedtherebetween, and at least some of the louvers of said another pluralityof louvers include second tabs with spaces located therebetween; andwherein at least some tabs from the plurality of louvers are positionedto cover at least some of the spaces between the another plurality oflouvers.
 15. The shield of claim 11 wherein: at least some of saidlouvers include tabs.
 16. In a reactor comprising an an electrode, areactor chamber, and a chuck that is adapted to hold a wafer, whichelectrode and chuck is located in the reactor chamber, the improvementcomprising: a shield which is located in the reactor chamber in theline-of-sight path between the chuck and the electrode, which shieldprevent the deposit of reaction materials from being directed backtoward the electrode.
 17. A shield for an inductively coupled reactorwhich is placed in the line-of-sight path between a portion of a chuckadapted to hold a wafer to be processed and an electrode in order toblock the path of material from the wafer directed toward a powertransfer window, said shield comprising: a plurality of louvers; andwherein said louvers are incorporated into the power transfer window.18. A shield for an inductively coupled reactor which is placed in theline-of-sight path between a portion of a chuck adapted to hold a waferto be processed and an electrode in order to block the path of materialfrom the wafer directed toward the electrode, said shield comprising: apower transfer window; a plurality of louvers; and wherein said louversare incorporated into the power transfer window.
 19. A shield for areactor which is placed in the line-of-sight path of a wafer to beprocessed and one of an electrode and a power transfer window in orderto block the path of material from the wafer directed toward said one ofsaid electrode and said power transfer window wherein said shield islocated substantially adjacent to said one of said electrode and saidpower transfer window, said shield comprising: a plurality of louvers.20. A shield for a reactor which is placed in the line-of-sight pathbetween a chuck which is adapted to hold a wafer to be processed and anelectrode in order to block the path of material from the wafer directedtoward the electrode, and said shield is located substantially adjacentto said electrode, said shield comprising: a plurality of louvers. 21.In a reactor comprising an electrode, a reactor chamber, and a chuckthat is adapted to hold a wafer, which electrode and chuck is located inthe reactor chamber, the improvement comprising: a shield which islocated in the reactor chamber in a line-of-sight path between the chuckand the electrode, which shield prevent the deposit of reactionmaterials from being directed back toward the electrode; and shield islocated adjacent to the electrode and wherein shield includes louvers.22. A shield for an inductively coupled reactor which is placed in aline-of-sight path between a portion of a chuck adapted to hold a waferto be processed and an electrode in order to block the path of materialfrom the wafer directed toward a power transfer window, said shieldcomprising: a plurality of louvers; and wherein said louvers are locatedadjacent to the power transfer window.
 23. A shield for an inductivelycoupled reactor which is placed in a line-of-sight path between aportion of a chuck adapted to hold a wafer to be processed and anelectrode in order to block the path of material from the wafer directedtoward the electrode, said shield comprising: a power transfer window; aplurality of louvers; and wherein said louvers are located adjacent tothe power transfer window.